It is the purpose of this project to study the invasive and immune mechanisms involved in sporozoite-induced infections in rodent (Plasmodium berghei) and simian (Plasmodium knowlesi) malaria. 1) Techniques are being developed to follow the course of sporozoite invasion in vitro and in vivo. 2) Cellular requirements for generating protection using T-and B-cell deficient mouse models have demonstrated the absolute dependency of T-cells in the protective immune responses against sporozoite infections. 3) Limited success was obtained in the immunization of Rhesus monkeys against P. knowlesi sporozoites.